The bvg or vir locus in B. pertussis is responsible for coordinate regulation of the virulence associated factors. Using TnphoA mutagenesis several vir activated genes (vags) have been identified. Some of these fusions were deficient in previously characterized factors such as pertussis toxin, or filamentous hemagglutinin. However one of these TnphoA fusion strains was defective in a 95kDa outer membrane protein. This strain has been shown to be unable to cause lymphocytosis or to persist in a mouse aerosol model of pertussis. The TnphoA insertion mutant has been used to isolate the wildtype gene, which is being sequenced. Purification of the protein has been initiated. A monoclonal immunization schedule has begun.